package com.fzy.leetcode.editor.cn;
//2023-03-18 20:33:52
//给你一个由 '1'（陆地）和 '0'（水）组成的的二维网格，请你计算网格中岛屿的数量。 
//
// 岛屿总是被水包围，并且每座岛屿只能由水平方向和/或竖直方向上相邻的陆地连接形成。 
//
// 此外，你可以假设该网格的四条边均被水包围。 
//
// 
//
// 示例 1： 
//
// 
//输入：grid = [
//  ["1","1","1","1","0"],
//  ["1","1","0","1","0"],
//  ["1","1","0","0","0"],
//  ["0","0","0","0","0"]
//]
//输出：1
// 
//
// 示例 2： 
//
// 
//输入：grid = [
//  ["1","1","0","0","0"],
//  ["1","1","0","0","0"],
//  ["0","0","1","0","0"],
//  ["0","0","0","1","1"]
//]
//输出：3
// 
//
// 
//
// 提示： 
//
// 
// m == grid.length 
// n == grid[i].length 
// 1 <= m, n <= 300 
// grid[i][j] 的值为 '0' 或 '1' 
// 
//
// Related Topics 深度优先搜索 广度优先搜索 并查集 数组 矩阵 👍 2112 👎 0

class NumberOfIslands {
    public static void main(String[] args) {
        //创建该题目的对象方便调用
        Solution solution = new NumberOfIslands().new Solution();
    }
    //leetcode submit region begin(Prohibit modification and deletion)
class Solution {
    public int numIslands(char[][] grid) {
        if(grid == null || grid.length == 0){
            return 0;
        }
        int m = grid.length;
        int n = grid[0].length;
        UnionFind uf = new UnionFind(grid);

        for(int i = 0;i<m;i++){
            for (int j = 0;j<n;j++){
                if(grid[i][j] == '1'){
                    grid[i][j] = '0';
                    if(i-1>=0 && grid[i-1][j] == '1'){
                        uf.union(i*n+j,(i-1)*n+j);
                    }
                    if(i+1<m && grid[i+1][j] == '1'){
                        uf.union(i*n+j,(i+1)*n+j);
                    }
                    if(j-1>=0 && grid[i][j-1] == '1'){
                        uf.union(i*n+j,i*n+j-1);
                    }
                    if(j+1<n && grid[i][j+1] == '1'){
                        uf.union(i*n+j,i*n+j+1);
                    }
                }
            }
        }

        return uf.getCount();
    }

    class UnionFind{

        int count;
        int[] parent;
        int[] rank;

        public UnionFind(char[][] grid){
            count = 0;
            int m = grid.length;
            int n = grid[0].length;
            parent = new int[m*n];
            rank = new int[m*n];

            for(int i = 0;i<m;i++){
                for(int j = 0;j<n;j++){
                    if(grid[i][j] == '1'){
                        parent[i*n+j] = i*n+j;
                        count++;
                    }
                    rank[i*n+j] = 0;
                }
            }
        }

        public int find(int i){
            if(parent[i] != i ){
                parent[i] = find(parent[i]);
            }
            return parent[i];
        }

        public void union(int x,int y){
            int rootx = find(x);
            int rooty = find(y);

            if(rootx != rooty){
                if(rank[rootx] > rank[rooty]){
                    parent[rooty] = rootx;
                }else if(rank[rootx] < rank[rooty]){
                    parent[rootx] = rooty;
                }else{
                    parent[rooty] = rootx;
                    rank[rootx] += 1;
                }
                count--;
            }
        }

        public int getCount(){
            return count;
        }
    }
}
//leetcode submit region end(Prohibit modification and deletion)

}